Angular velocity detection circuit

ABSTRACT

An angular velocity detection apparatus includes a vibrator that generates a signal that includes an angular velocity component and a vibration leakage component, a driver section that generates the drive signal, and supplies the drive signal to the vibrator, an angular velocity signal generation section that extracts the angular velocity component from the signal generated by the vibrator, and generates an angular velocity signal corresponding to the magnitude of the angular velocity component, a vibration leakage signal generation section that extracts the vibration leakage component from the signal generated by the vibrator, and generates a vibration leakage signal corresponding to the magnitude of the vibration leakage component, and an adder-subtractor section that adds the vibration leakage signal to the angular velocity signal, or subtracts the vibration leakage signal from the angular velocity signal, in a given ratio to correct temperature characteristics of the angular velocity signal.

This application is a continuation application of U.S. application Ser.No. 13/216,553 filed Aug. 24, 2011 which claims priority to JapanesePatent Application No. 2010-199791 filed on Sep. 7, 2010 all of whichare hereby incorporated by reference in their entireties.

BACKGROUND OF THE INVENTION

The present invention relates to an angular velocity detection apparatusand an electronic instrument.

An electronic instrument or a system that includes an angular velocitydetection apparatus, and performs a predetermined control process basedon the angular velocity detected by the angular velocity detectionapparatus has been widely used. For example, a vehicle travel controlsystem prevents a side skid, or detects an overturn, based on theangular velocity detected by the angular velocity detection apparatus.

Such an electronic instrument or system performs wrong control if theangular velocity detection apparatus breaks down. Therefore, measuressuch as lighting an alarm lamp when the angular velocity detectionapparatus has broken down have been employed. Various technologies thatdiagnose failure of the angular velocity detection apparatus have beenproposed. For example, JP-A-2000-171257 focuses on the fact that asignal output from the vibrator of the angular velocity detectionapparatus includes an angular velocity component, and a self-vibrationcomponent (vibration leakage component) based on excited vibrations ofthe vibrator, and discloses method that determines the presence orabsence of failure of the angular velocity detection apparatus byextracting the vibration leakage component from the signal output fromthe vibrator, and monitoring the amplitude of the vibration leakagecomponent. JP-A-2010-107416 discloses a failure diagnosis method thatreliably generates a self-vibration component by tuning the balance sothat the vibration energy of the vibrator becomes imbalanced.

It is ideal that a circuit that extracts the angular velocity componentnot to extract the vibration leakage component. However, a phase shiftof a synchronous detection clock signal occurs due to a circuitproduction variation, so that the vibration leakage component isincluded in the extracted angular velocity signal (gyro signal).Therefore, if the vibration leakage component is enhanced as disclosedin JP-A-2010-107416, the temperature characteristics of the angularvelocity signal deteriorate due to the effect of the temperaturecharacteristics of the vibration leakage component. If the temperaturecharacteristics of the vibration leakage component are indicated by alinear function or a quadratic function, the temperature characteristicsof the vibration leakage component can be corrected using a small-scaletemperature compensation circuit. However, the vibration leakagecomponent has temperature characteristics indicated by a higher-orderfunction. The circuit scale necessarily increases when correcting thetemperature characteristics of the vibration leakage component using ahigher-order function circuit.

SUMMARY

According to a first aspect of the invention, there is provided anangular velocity detection apparatus including:

a vibrator that generates a signal that includes an angular velocitycomponent corresponding to the magnitude of an angular velocity, and avibration leakage component of vibrations based on a drive signal;

a driver section that generates the drive signal, and supplies the drivesignal to the vibrator;

an angular velocity signal generation section that extracts the angularvelocity component from the signal generated by the vibrator, andgenerates an angular velocity signal corresponding to the magnitude ofthe angular velocity component;

a vibration leakage signal generation section that extracts thevibration leakage component from the signal generated by the vibrator,and generates a vibration leakage signal corresponding to the magnitudeof the vibration leakage component; and

an adder-subtractor section that adds the vibration leakage signal tothe angular velocity signal, or subtracts the vibration leakage signalfrom the angular velocity signal, in a given ratio to correcttemperature characteristics of the angular velocity signal.

According to a second aspect of the invention, there is provided anelectronic instrument including the above angular velocity detectionapparatus.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a diagram illustrating a configuration example of an angularvelocity detection apparatus according to a first embodiment of theinvention.

FIG. 2 is a diagram illustrating a vibrating element of a gyro sensorelement.

FIG. 3 is a diagram illustrating the operation of a gyro sensor element.

FIG. 4 is a diagram illustrating the operation of a gyro sensor element.

FIG. 5 is a waveform diagram illustrating the angular velocity detectionprinciple.

FIG. 6 is a waveform diagram illustrating the vibration leak detectionprinciple.

FIGS. 7A to 7C are graphs illustrating an example of the temperaturecharacteristics of an angular velocity signal and the temperaturecharacteristics of a vibration leakage signal.

FIGS. 8A to 8C are graphs illustrating an example of the temperaturecharacteristics of an angular velocity signal and the temperaturecharacteristics of a vibration leakage signal.

FIG. 9 is a diagram illustrating a configuration example of anadder-subtractor circuit.

FIGS. 10A to 10D are graphs illustrating an example of correction of thetemperature characteristics of an angular velocity signal according tothe first embodiment.

FIGS. 11A to 11D are graphs illustrating an example of correction of thetemperature characteristics of an angular velocity signal according tothe first embodiment.

FIG. 12 is a graph illustrating an example of the temperaturecharacteristics of an angular velocity signal and the temperaturecharacteristics of a vibration leakage signal.

FIG. 13 is a diagram illustrating a configuration example of an angularvelocity detection apparatus according to a second embodiment of theinvention.

FIG. 14 is a diagram illustrating a configuration example of afirst-order temperature adjustment circuit.

FIGS. 15A to 15F are graphs illustrating an example of correction of thetemperature characteristics of an angular velocity signal according tothe second embodiment.

FIG. 16 is a diagram illustrating a configuration example of an angularvelocity detection apparatus according to a third embodiment of theinvention.

FIGS. 17A to 17E are graphs illustrating an example of correction of thetemperature characteristics of an angular velocity signal according tothe third embodiment.

FIG. 18 is a diagram illustrating a configuration example of an angularvelocity detection apparatus according to a fourth embodiment of theinvention.

FIGS. 19A to 19F are graphs illustrating an example of correction of thetemperature characteristics of an angular velocity signal according tothe fourth embodiment.

FIG. 20 is a functional block diagram of an electronic instrument.

DETAILED DESCRIPTION OF THE EMBODIMENT

The invention may provide an angular velocity detection apparatus and anelectronic instrument that can compensate for a change in temperaturecharacteristics of the angular velocity signal due to the vibrationleakage component without using a higher-order temperature compensationcircuit.

(1) According to one embodiment of the invention, there is provided anangular velocity detection apparatus including:

a vibrator that generates a signal that includes an angular velocitycomponent corresponding to the magnitude of an angular velocity, and avibration leakage component of vibrations based on a drive signal;

a driver section that generates the drive signal, and supplies the drivesignal to the vibrator;

an angular velocity signal generation section that extracts the angularvelocity component from the signal generated by the vibrator, andgenerates an angular velocity signal corresponding to the magnitude ofthe angular velocity component;

a vibration leakage signal generation section that extracts thevibration leakage component from the signal generated by the vibrator,and generates a vibration leakage signal corresponding to the magnitudeof the vibration leakage component; and

an adder-subtractor section that adds the vibration leakage signal tothe angular velocity signal, or subtracts the vibration leakage signalfrom the angular velocity signal, in a given ratio to correcttemperature characteristics of the angular velocity signal.

The angular velocity signal generation section may extract the angularvelocity component from the signal generated by the vibrator based on afirst detection signal that is synchronized with the drive signal, forexample. The vibration leakage signal generation section may extract thevibration leakage component from the signal generated by the vibratorbased on a second detection signal that is synchronized with the drivesignal and differs in phase from the first detection signal, forexample.

According to the above embodiment, the temperature characteristics ofthe angular velocity signal can be corrected by adding the vibrationleakage signal to the angular velocity signal, or subtracting thevibration leakage signal from the angular velocity signal, in a givenratio, on the assumption that the temperature characteristics of theangular velocity signal and the temperature characteristics of thevibration leakage signal have a correlation. This makes it possible tocompensate for a change in temperature characteristics of the angularvelocity signal due to the vibration leakage component without using ahigher-order temperature compensation circuit.

(2) The above angular velocity detection apparatus may further include afirst first-order temperature adjustment section that adjusts afirst-order component of the temperature characteristics of the angularvelocity signal input to the adder-subtractor section to approach afirst value, and a second first-order temperature adjustment sectionthat adjusts a first-order component of temperature characteristics ofthe vibration leakage signal input to the adder-subtractor section toapproach a second value.

The first value and the second value may be selected based on therelationship between the temperature characteristics of the angularvelocity signal and the temperature characteristics of the vibrationleakage signal so that the temperature characteristics of the angularvelocity signal are corrected by addition or subtraction by theadder-subtractor section. For example, the first value and the secondvalue may be set to an identical value when the temperaturecharacteristic curve of the angular velocity signal and the temperaturecharacteristic curve of the vibration leakage signal bend similarly, andthe adder-subtractor section may subtract the vibration leakage signalfrom the angular velocity signal in the given ratio. The first value andthe second value may be set to values that differ in sign and have thesame absolute value when the temperature characteristic curve of theangular velocity signal and the temperature characteristic curve of thevibration leakage signal bend in an opposite way, and theadder-subtractor section may add the vibration leakage signal to theangular velocity signal in the given ratio.

This makes it possible to implement a temperature compensation processon the angular velocity signal even when the first-order component ofthe temperature characteristics of the angular velocity signal and thefirst-order component of the temperature characteristics of thevibration leakage signal differ to a large extent.

(3) The above angular velocity detection apparatus may further include afirst-order temperature adjustment section that adjusts one of afirst-order component of the temperature characteristics of the angularvelocity signal input to the adder-subtractor section and a first-ordercomponent of temperature characteristics of the vibration leakage signalinput to the adder-subtractor section to approach the other of thefirst-order component of the temperature characteristics of the angularvelocity signal and the first-order component of the temperaturecharacteristics of the vibration leakage signal.

This makes it possible to implement a temperature compensation processon the angular velocity signal even when the first-order component ofthe temperature characteristics of the angular velocity signal and thefirst-order component of the temperature characteristics of thevibration leakage signal differ to a large extent.

(4) The above angular velocity detection apparatus may further include afirst-order temperature correction section that corrects a first-ordercomponent of temperature characteristics of a signal obtained by theadder-subtractor section.

This makes it possible to implement a more accurate temperaturecompensation process on the angular velocity signal even when thefirst-order component of the temperature characteristics of the angularvelocity signal and the first-order component of the temperaturecharacteristics of the vibration leakage signal differ to a largeextent.

(5) The above angular velocity detection apparatus may further include aterminal that outputs a signal based on the vibration leakage signal tothe outside.

The signal based on the vibration leakage signal may be the vibrationleakage signal, or may be a signal obtained by performing a specificprocess (e.g., amplification) on the vibration leakage signal.

The presence or absence of failure of the angular velocity detectionapparatus can be externally determined by monitoring the signal based onthe vibration leakage signal on the assumption that the amplitude of thevibration leakage component is constant independently of the angularvelocity.

(6) The above angular velocity detection apparatus may further include afailure determination section that determines the presence or absence offailure of the angular velocity detection apparatus based on thevibration leakage signal.

This makes it possible for the angular velocity detection apparatus todetermine the presence or absence of failure of the angular velocitydetection apparatus. If the determination result signal of the failuredetermination section is output to the outside, the presence or absenceof failure of the angular velocity detection apparatus can be externallydetermined by monitoring the signal output from the failuredetermination section.

(7) In the above angular velocity detection apparatus, theadder-subtractor section may include an inverting amplifier that invertsa polarity of an input signal, a switch circuit that selects whether ornot to bypass the inverting amplifier, and a variable gain amplifierthat is disposed in series with the inverting amplifier, and amplifiesor attenuates an input signal by a gain that can be variably set, mayselect whether or not to add a signal obtained by inverting a polarityof the vibration leakage signal to the angular velocity signal using theinverting amplifier and the switch circuit, and may select a ratio ofthe vibration leakage signal added to the angular velocity signal usingthe variable gain amplifier.

This makes it possible to select whether or not to invert the polarityof the vibration leakage signal based on the connection setting of theswitch circuit, and amplify or attenuate the vibration leakage signal tothe desired level based on the gain setting of the variable gainamplifier. Therefore, even if the level or the polarity of thetemperature characteristics of the vibration leakage signal varies, thetemperature characteristics of the vibration leakage signal can becaused to approach the temperature characteristics of the angularvelocity signal or temperature characteristics obtained by inverting thepolarity of the temperature characteristics of the angular velocitysignal. This makes it possible to implement a temperature compensationprocess on the angular velocity signal.

(8) According to another embodiment of the invention, there is providedan electronic instrument including the above angular velocity detectionapparatus.

Exemplary embodiments of the invention are described in detail belowwith reference to the drawings. Note that the following embodiments donot unduly limit the scope of the invention as stated in the claims.Note also that all of the elements described below should notnecessarily be taken as essential elements of the invention.

1. ANGULAR VELOCITY DETECTION APPARATUS 1-1. First Embodiment

FIG. 1 is a diagram illustrating a configuration example of an angularvelocity detection apparatus according to a first embodiment of theinvention.

An angular velocity detection apparatus 1 according to the firstembodiment includes a gyro sensor element 100 and an angular velocitydetection IC 10.

The gyro sensor element 100 (i.e., vibrator) includes a vibratingelement that includes a drive electrode and a detection electrode and issealed in a package (not shown). The package normally has seal-tightnessin order to reduce the impedance of the vibrating element to improve thevibration efficiency as much as possible.

The vibrating element of the gyro sensor element 100 may be formed of apiezoelectric material such as a piezoelectric single crystal (e.g.,quartz crystal (SiO₂), lithium tantalate (LiTaO₃), or lithium niobate(LiNbO₃)) or a piezoelectric ceramic (e.g., lead zirconate titanate(PZT)), or may have a structure in which a piezoelectric thin film(e.g., zinc oxide (ZnO) or aluminum nitride (AlN)) is disposed betweenthe drive electrodes on the surface of semiconductor silicon.

In this embodiment, the gyro sensor element 100 is formed using adouble-T-shaped vibrating element that includes two T-shaped drivevibrating arms. The vibrating element may have a tuning-fork structure,or a tuning-bar structure in the shape of a triangular prism, aquadrangular prism, or a column, for example.

FIG. 2 is a diagram illustrating the vibrating element of the gyrosensor element 100 according to this embodiment.

The gyro sensor element 100 according to this embodiment includes adouble-T-shaped vibrating element that is formed using a Z-cut quartzcrystal substrate. A vibrating element formed of a quartz crystal has anadvantage in that the angular velocity detection accuracy can beimproved since the resonance frequency changes to only a small extentdue to a change in temperature. Note that the X-axis, the Y-axis, andthe Z-axis illustrated in FIG. 2 indicate the axes of the quartzcrystal.

As illustrated in FIG. 2, the vibrating element of the gyro sensorelement 100 includes drive vibrating arms 101 a and 101 b that extendrespectively from drive bases 104 a and 104 b in the +Y-axis directionand the −Y-axis direction. Drive electrodes 112 and 113 are respectivelyformed on the side surface and the upper surface of the drive vibratingarm 101 a, and drive electrodes 113 and 112 are respectively formed onthe side surface and the upper surface of the drive vibrating arm 101 b.The drive electrodes 112 and 113 are connected to a driver circuit 20respectively via an external output terminal 11 and an external inputterminal 12 of the angular velocity detection IC 10 illustrated in FIG.1.

The drive bases 104 a and 104 b are connected to a rectangular detectionbase 107 via connection arms 105 a and 105 b that respectively extend inthe −X-axis direction and the +X-axis direction.

Detection vibrating arms 102 extend from the detection base 107 in the+Y-axis direction and the −Y-axis direction. Detection electrodes 114and 115 are formed on the upper surface of the detection vibrating arms102, and common electrodes 116 are formed on the side surface of thedetection vibrating arms 102. The detection electrodes 114 and 115 areconnected to a detection circuit 30 respectively via external inputterminals 13 and 14 of the angular velocity detection IC 10 illustratedin FIG. 1. The common electrodes 116 are grounded.

When an alternating voltage (drive signal) is applied between the driveelectrodes 112 and 113 of the drive vibrating arms 101 a and 101 b, thedrive vibrating arms 101 a and 101 b produce flexural vibrations(excited vibrations) so that the ends of the drive vibrating arms 101 aand 101 b repeatedly move closer and away (see arrow B) due to aninverse piezoelectric effect (see FIG. 3).

When an angular velocity around the Z-axis is applied to the vibratingelement of the gyro sensor element 100, the drive vibrating arms 101 aand 101 b are subjected to a Coriolis force in the direction that isperpendicular to the direction of the flexural vibrations (see arrow B)and the Z-axis. Therefore, the connection arms 105 a and 105 b producevibrations (see arrow C), as illustrated in FIG. 4. The detectionvibrating arms 102 produce flexural vibrations (see arrow D) insynchronization with the vibrations (see arrow C) of the connection arms105 a and 105 b. The vibrations of the detection vibrating arms 102based on the Coriolis force differ in phase from the flexural vibrations(excited vibrations) of the drive vibrating arms 101 a and 101 b by 90°.

The vibration energy of the drive vibrating arms 101 a and 101 b isbalanced when the magnitude of the vibration energy or the vibrationamplitude of the drive vibrating arms 101 a and 101 b is equal when thedrive vibrating arms 101 a and 101 b produce flexural vibrations(excited vibrations), and the detection vibrating arm 102 does notproduce flexural vibrations in a state in which an angular velocity isnot applied to the gyro sensor element 100. However, when the balance ofthe vibration energy of the drive vibrating arms 101 a and 101 b islost, the detection vibrating arm 102 produces flexural vibrations evenif an angular velocity is not applied to the gyro sensor element 100.The above flexural vibrations are referred to as leakage vibrations. Theleakage vibrations are flexural vibrations (see arrow D) in the samemanner as the vibrations based on the Coriolis force, but occur in thesame phase as the drive signal.

An alternating charge based on the flexural vibrations occurs in thedetection electrodes 114 and 115 of the detection vibrating arms 102 dueto a piezoelectric effect. An alternating charge that is generated basedon the Coriolis force changes depending on the magnitude of the Coriolisforce (i.e., the magnitude of the angular velocity applied to the gyrosensor element 100). On the other hand, an alternating charge that isgenerated based on the leakage vibrations is constant independently ofthe magnitude of the angular velocity applied to the gyro sensor element100.

A rectangular weight section 103 that is wider than the drive vibratingarms 101 a and 101 b is formed at the end of the drive vibrating arms101 a and 101 b. This makes it possible to increase the Coriolis forcewhile obtaining the desired resonance frequency using relatively shortvibrating arms. A weight section 106 that is wider than the detectionvibrating arms 102 is formed at the end of the detection vibrating arm102. This makes it possible to increase the amount of alternating chargethat flows through the detection electrodes 114 and 115.

The gyro sensor element 100 thus outputs an alternating charge (i.e.,angular velocity component) that is generated based on the Coriolisforce and an alternating charge (i.e., vibration leakage component) thatis generated based on the leakage vibrations of the excited vibrationsvia the detection electrodes 114 and 115 (detection axis: Z-axis).

A Coriolis force F_(c) applied to the gyro sensor element 100 iscalculated by the following expression (1):

F _(c)=2mvΩ  (1)

where, m is an equivalent mass, v is a vibration velocity, and omega isan angular velocity. As is clear from the expression (1), the Coriolisforce changes due to a change in equivalent mass m or vibration velocityv, even if the angular velocity omega is constant. Specifically, theangular velocity detection sensitivity changes due to a change inequivalent mass m or vibration velocity v. When the vibration state ofthe vibrating element of the gyro sensor element 100 has changed due tofailure, the equivalent mass m or the vibration velocity v of thedriving vibrations changes, so that the detection sensitivity changes.The state of the leakage vibrations also changes due to a change inequivalent mass m or vibration velocity v, so that the magnitude of thevibration leakage component changes. Specifically, the magnitude of thevibration leakage component has a correlation with the angular velocitydetection sensitivity, and the presence or absence of failure of thegyro sensor element 100 can be determined by monitoring the magnitude ofthe vibration leakage component.

In this embodiment, the vibration leakage component at the desired levelis positively generated by causing the balance of the vibration energyof the drive vibrating arms 101 a and 101 b to be lost to some extent.In particular, since the gyro sensor element 100 is formed using thedouble-T-shaped vibrating element, it is easy to cause the flexuralvibrations of the drive vibrating arm 101 a and the flexural vibrationsof the drive vibrating arm 101 b to become imbalanced by varying themass of the weight section 103 at the end of the drive vibrating arm 101a and the weight section 103 at the end of the drive vibrating arm 101b.

Again referring to FIG. 1, the angular velocity detection IC 10 includesthe driver circuit 20, the detection circuit 30, a reference powersupply circuit 40, and a memory 50.

The driver circuit 20 includes an I/V conversion circuit(current/voltage conversion circuit) 210, an AC amplifier circuit 220,and an amplitude adjustment circuit 230.

The I/V conversion circuit 210 converts a drive current that flowsthrough the vibrating element of the gyro sensor element 100 into analternating voltage signal.

The alternating voltage signal output from the I/V conversion circuit210 is input to the AC amplifier circuit 220 and the amplitudeadjustment circuit 230. The AC amplifier circuit 220 amplifies thealternating voltage signal input thereto, clips the signal to apredetermined voltage value, and outputs a square-wave voltage signal22. The amplitude adjustment circuit 230 changes the amplitude of thesquare-wave voltage signal 22 based on the level of the alternatingvoltage signal output from the I/V conversion circuit 210, and controlsthe AC amplifier circuit 220 so that a constant drive current ismaintained.

The square-wave voltage signal 22 is supplied to the drive electrode 112of the vibrating element of the gyro sensor element 100 via the externaloutput terminal 11. The gyro sensor element 100 continuously producespredetermined driving vibrations (see FIG. 3). The drive vibrating arms101 a and 101 b of the gyro sensor element 100 produce vibrations at aconstant velocity by maintaining a constant drive current. Therefore,the vibration velocity based on which the Coriolis force is producedbecomes constant, so that the sensitivity is further stabilized.

The detection circuit 30 includes charge amplifiers 310 and 312, adifferential amplifier circuit 320, an AC amplifier circuit 330, a phaseshift circuit 340, synchronous detection circuits 350 and 352,integration circuits 360 and 362, an adder-subtractor circuit 370, andDC amplifier circuits 380 and 382.

An alternating charge that includes the angular velocity component andthe vibration leakage component is input to the charge amplifier 310from the detection electrode 114 of the vibrating element of the gyrosensor element 100 via the external input terminal 13.

An alternating charge that includes the angular velocity component andthe vibration leakage component is input to the charge amplifier 312from the detection electrode 115 of the vibrating element of the gyrosensor element 100 via the external input terminal 14.

Each of the charge amplifiers 310 and 312 converts the alternatingcharge input thereto into an alternating voltage signal based on areference voltage V_(ref). The reference power supply circuit 40generates the reference voltage V_(ref) based on an external powersupply voltage input via a power supply input terminal 15.

The differential amplifier circuit 320 differentially amplifies thesignal output from the charge amplifier 310 and the signal output fromthe charge amplifier 312. The differential amplifier circuit 320 removesan in-phase component, and amplifies an out-of-phase component.

The AC amplifier circuit 330 amplifies the signal output from thedifferential amplifier circuit 330. A signal output from the ACamplifier circuit 330 includes the angular velocity component and thevibration leakage component, and is input to the synchronous detectioncircuits 350 and 352 as a detection target signal 33.

The synchronous detection circuit 350 performs a synchronous detectionprocess on the detection target signal 33 using the square-wave voltagesignal 22 as a detection signal. The synchronous detection circuit 350may be configured as a switch circuit that selects the detection targetsignal 33 when the voltage level of the square-wave voltage signal 22 ishigher than the reference voltage V_(ref), and selects a signal obtainedby inverting the detection target signal 33 with respect to thereference voltage V_(ref) when the voltage level of the square-wavevoltage signal 22 is lower than the reference voltage V_(ref).

The synchronous detection circuit 352 performs a synchronous detectionprocess on the detection target signal 33 using a square-wave voltagesignal 34 that is obtained by delaying the phase of the square-wavevoltage signal 22 by 90° using the phase shift circuit 340 as adetection signal. The synchronous detection circuit 352 may beconfigured as a switch circuit that selects the detection target signal33 when the voltage level of the square-wave voltage signal 34 is higherthan the reference voltage V_(ref), and selects a signal obtained byinverting the detection target signal 33 with respect to the referencevoltage V_(ref) when the voltage level of the square-wave voltage signal34 is lower than the reference voltage V_(ref).

The signal output from the synchronous detection circuit 350 is smoothedinto a direct voltage signal by the smoothing circuit 360, and input tothe adder-subtractor circuit 370 as an angular velocity signal 36 a.

The signal output from the synchronous detection circuit 352 is smoothedinto a direct voltage signal by the integration circuit 362, and inputto the adder-subtractor circuit 370 and the DC amplifier circuit 382 asa vibration leakage signal 36 b.

The adder-subtractor circuit 370 adds the vibration leakage signal 36 bto the angular velocity signal 36 a, or subtracts the vibration leakagesignal 36 b from the angular velocity signal 36 a in a preset ratio.

The DC amplifier circuit 380 amplifies or attenuates the angularvelocity signal 37 that has been corrected in temperaturecharacteristics by the adder-subtractor circuit 370 so that the desiredlevel is achieved. An external apparatus (not shown) can obtain angularvelocity information by monitoring the angular velocity signal 38 a.

The DC amplifier circuit 382 amplifies or attenuates the vibrationleakage signal 36 b so that the desired level is achieved, and outputsthe resulting signal to the outside as a vibration leakage signal 38 bvia an external output terminal 17. An external apparatus (not shown)can determine the presence or absence of failure, disconnection, or thelike of the gyro sensor element 100 by monitoring the vibration leakagesignal 38 b.

The angular velocity detection IC 10 may include a failure determinationcircuit 60 that determines the presence or absence of failure of theangular velocity detection apparatus 1. The failure determinationcircuit 60 determines the presence or absence of failure of the angularvelocity detection apparatus 1 based on the vibration leakage signal 36b, and outputs a failure determination signal 62 to the outside via anexternal output terminal 18. The failure determination circuit 60 maydetermine that the angular velocity detection apparatus 1 is normal(without failure) when the amplitude of the vibration leakage signal 36b is within a predetermined range, and may determine that failure hasoccurred in the angular velocity detection apparatus 1 when theamplitude of the vibration leakage signal 36 b is outside thepredetermined range, for example. Since the amplitude of the vibrationleakage signal 36 b varies depending on the sample, a failuredetermination reference value may be stored in the memory 50.

Note that the driver circuit 20 functions as a driver section. Thesynchronous detection circuit 350 and the integration circuit 360function as an angular velocity signal generation section. Note that thesynchronous detection circuit 350 and the signal output from thesynchronous detection circuit 350 may serve as the angular velocitysignal generation section and the angular velocity signal, respectively.The synchronous detection circuit 350 and the integration circuit 360function as a vibration leakage signal generation section. Note that thesynchronous detection circuit 350 and the signal output from thesynchronous detection circuit 350 may serve as the vibration leakagesignal generation section and the vibration leakage signal,respectively. The adder-subtractor circuit 370 function as anadder-subtractor section. The failure determination circuit 60 functionsas a failure determination section.

The angular velocity detection principle of the angular velocitydetection apparatus illustrated in FIG. 1 is described below withreference to FIG. 5 (waveform diagram). FIG. 5 illustrates an example ofthe signal waveforms at points A to J illustrated in FIG. 1. In FIG. 5,the horizontal axis indicates time, and the vertical axis indicatesvoltage.

When the vibrating element of the gyro sensor element 100 vibrates, analternating voltage that has a constant frequency and is obtained byconverting a current that is fed back from the drive electrode 113 ofthe vibrating element of the gyro sensor element 100 is generated at theoutput (point A) of the UV conversion circuit 210. Specifically, asine-wave voltage signal that has a constant frequency is generated atthe output (point A) of the UV conversion circuit 210.

The square-wave voltage signal 22 that has a constant amplitude V_(c)and is obtained by amplifying the signal output from the UV conversioncircuit 210 (signal at the point A) is generated at the output (point B)of the AC amplifier circuit 220.

When an angular velocity is applied to the gyro sensor element 100, asignal that includes the angular velocity component and the vibrationleakage component flows through the detection electrodes 114 and 115 ofthe vibrating element of the gyro sensor element 100. The magnitude ofthe angular velocity component changes depending on the magnitude of theCoriolis force. On the other hand, the vibration leakage component isconstant independently of the magnitude of the angular velocity. FIG. 5illustrates the signal waveforms that focus only on the angular velocitycomponent since FIG. 5 is used to describe the angular velocitydetection principle. The following description also focuses only on theangular velocity component.

The angular velocity components (alternating charge) that flow throughthe detection electrodes 114 and 115 of the vibrating element of thegyro sensor element 100 are converted into alternating voltage signalsby the charge amplifiers 310 and 312. Therefore, sine-wave voltagesignals having the same frequency as that of the signal output from theAC amplifier circuit 220 (signal at the point B) are generated at theoutputs (points C and D) of the charge amplifiers 310 and 312. The phaseof the signal output from the charge amplifier 310 (signal at the pointC) is the same as the phase of the signal output from the AC amplifiercircuit 220 (signal at the point B). The phase of the signal output fromthe charge amplifier 312 (signal at the point D) is the reverse of(shifted by 180° from) the phase of the signal output from the chargeamplifier circuit 310 (signal at the point C).

The signals output from the charge amplifiers 310 and 312 (signals atthe points C and D) are differentially amplified by the differentialamplifier circuit 320, and a sine-wave voltage signal that has the samefrequency and the same phase as those of the sine-wave voltage signalgenerated at the output (point C) of the charge amplifier circuit 310 isgenerated at the output (point E) of the AC amplifier circuit 330. Thesine-wave voltage signal that is generated at the output (point E) ofthe AC amplifier circuit 330 is a signal obtained by amplifying theangular velocity component of the signal that flows through thedetection electrodes 114 and 115 of the gyro sensor element 100.

The signal output from the AC amplifier circuit 330 (signal at the pointE) is synchronously detected by the synchronous detection circuit 350based on the square-wave voltage signal 22. Since the phase of thesignal output from the AC amplifier circuit 330 (signal at the point E)is the same as the phase of the square-wave voltage signal 22 (signal atthe point B), the signal output from the synchronous detection circuit350 (signal at the point G) is a signal that is obtained by full-waverectifying the signal output from the AC amplifier circuit 330 (signalat the point E). Therefore, a direct voltage signal (i.e., angularvelocity signal 36 a) that has a voltage value V₁ corresponding to themagnitude of the angular velocity is generated at the output (point H)of the integration circuit 360.

The square-wave voltage signal 34 that is delayed in phase by 90° withrespect to the square-wave voltage signal 22 (signal at the point B) isgenerated at the output (point F) of the phase shift circuit 340, andthe signal output from the AC amplifier circuit 330 (signal at the pointE) is synchronously detected by the synchronous detection circuit 352based on the square-wave voltage signal 34. Since the phase of thesignal output from the AC amplifier circuit 330 (signal at the point E)is shifted from the phase of the square-wave voltage signal 34 (signalat the point F) by 90°, the signal output from the synchronous detectioncircuit 352 (signal at the point I) is characterized in that theintegral quantity of the voltage that is higher than the referencevoltage V_(ref) is equal to the integral quantity of the voltage that islower than the reference voltage V_(ref). Therefore, the angularvelocity component is canceled, and a direct voltage signal that is setat the reference voltage V_(ref) is generated at the output (point J) ofthe integration circuit 362.

When an angular velocity is applied to the angular velocity detectionapparatus 1 in the direction opposite to the direction illustrated inFIG. 5, the waveform of the signal output from the charge amplifier 310(signal at the point C) and the waveform of the signal output from thecharge amplifier 312 (signal at the point D) are inverted with respectto the reference voltage V_(ref). Therefore, the angular velocity signal36 a (signal at the point H) is set at a voltage lower than thereference voltage V_(ref). Since the voltage value of the angularvelocity signal 36 a is proportional to the magnitude of the Coriolisforce (magnitude of the angular velocity), and the polarity of theangular velocity signal 36 a is determined by the rotation direction,the angular velocity applied to the angular velocity detection apparatus1 can be calculated based on the angular velocity signal 36 a.

The vibration leakage detection principle of the angular velocitydetection apparatus illustrated in FIG. 1 is described below withreference to FIG. 6 (waveform diagram). FIG. 6 illustrates an example ofthe signal waveforms at the points A to J illustrated in FIG. 1. In FIG.6, the horizontal axis indicates time, and the vertical axis indicatesvoltage.

The signal waveforms at the points A, B, and F are the same as thoseillustrated in FIG. 5. Therefore, description thereof is omitted. FIG. 5illustrates the signal waveforms that focus only on the vibrationleakage component since FIG. 6 is used to describe the vibration leakagedetection principle. The following description also focuses only on thevibration leakage component.

The vibration leakage components (alternating charge) that flow throughthe detection electrodes 114 and 115 of the vibrating element of thegyro sensor element 100 are converted into alternating voltage signalsby the charge amplifier circuits 310 and 312. Therefore, sine-wavevoltage signals having the same frequency as that of the signal outputfrom the AC amplifier circuit 220 (signal at the point B) are generatedat the outputs (points C and D) of the charge amplifiers 310 and 312.The phase of the signal output from the charge amplifier 310 (signal atthe point C) is shifted from the phase of the signal output from the ACamplifier circuit 220 (signal at the point B) by 90°. The phase of thesignal output from the charge amplifier 312 (signal at the point D) isthe reverse of (shifted by 180° from) the phase of the signal outputfrom the charge amplifier circuit 310 (signal at the point C).

The signals output from the charge amplifiers 310 and 312 (signals atthe points C and D) are differentially amplified by the differentialamplifier circuit 320, and a sine-wave voltage signal that has the samefrequency and the same phase as those of the sine-wave voltage signalgenerated at the output (point C) of the charge amplifier circuit 310 isgenerated at the output (point E) of the AC amplifier circuit 330. Thesine-wave voltage signal that is generated at the output (point E) ofthe AC amplifier circuit 330 is a signal obtained by amplifying thevibration leakage component of the signal that flows through thedetection electrodes 114 and 115 of the gyro sensor element 100.

The signal output from the AC amplifier circuit 330 (signal at the pointE) is synchronously detected by the synchronous detection circuit 350based on the square-wave voltage signal 22. Since the phase of thesignal output from the AC amplifier circuit 330 (signal at the point E)is shifted from the phase of the square-wave voltage signal 22 (signalat the point B) by 90°, the signal output from the synchronous detectioncircuit 352 (signal at the point I) is characterized in that theintegral quantity of the voltage that is higher than the referencevoltage V_(ref) is equal to the integral quantity of the voltage that islower than the reference voltage V_(ref). Therefore, the vibrationleakage component is canceled, and a direct voltage signal that is setat the reference voltage V_(ref) is generated at the output (point H) ofthe integration circuit 360.

The signal output from the AC amplifier circuit 330 (signal at the pointE) is synchronously detected by the synchronous detection circuit 352based on the square-wave voltage signal 34. Since the phase of thesignal output from the AC amplifier circuit 330 (signal at the point E)is the same as the phase of the square-wave voltage signal 34 (signal atthe point F), the signal output from the synchronous detection circuit352 (signal at the point I) is a signal that is obtained by full-waverectifying the signal output from the AC amplifier circuit 330 (signalat the point E). Therefore, a direct voltage signal (i.e., vibrationleakage signal 36 b) that has a voltage value V₂ corresponding to themagnitude of the vibration leakage component is generated at the output(point J) of the integration circuit 362.

The voltage value of the vibration leakage signal 36 b is proportionalto the magnitude of the vibration leakage component. Since the magnitudeof the vibration leakage component is constant when failure has notoccurred, the presence or absence of failure of the angular velocitydetection apparatus 1 can be determined by monitoring the vibrationleakage signal 36 b.

An ideal detection principle has been described with reference to FIGS.5 and 6 on the assumption that the vibration energy of the drivevibrating arms 101 a and 101 b is balanced, and the phase shift circuit340 accurately delays the phase by 90°. However, the balance of thevibration energy varies depending on the gyro sensor element, and thephase shifted by the phase shift circuit 340 also varies depending onthe IC. Therefore, the vibration leakage component is detected by thesynchronous detection circuit 350, and the angular velocity signal 36 aincludes an offset due to the vibration leakage component. If the offsetis constant independently of the temperature, the offset can becorrected by an offset adjustment circuit (zero-point adjustmentcircuit) (not shown). However, the angular velocity signal 36 a does nothave flat temperature characteristics. In the angular velocity detectionapparatus 1 according to this embodiment, the adder-subtractor circuit370 is provided in the subsequent stage of the integration circuit 360to correct the temperature characteristics of the angular velocitysignal 36 a. Specifically, since the temperature characteristics of theangular velocity signal 36 a have a correlation with the temperaturecharacteristics of the vibration leakage signal 36 b, theadder-subtractor circuit 370 corrects the temperature characteristics ofthe angular velocity signal 36 a using the vibration leakage signal 36b.

FIGS. 7A to 7C and FIGS. 8A to 8C are graphs illustrating an example ofthe temperature characteristics of the angular velocity signal 36 a andthe temperature characteristics of the vibration leakage signal 36 b ofsix samples of the angular velocity detection apparatus 1 when theangular velocity detection apparatus 1 is stationary (i.e., an angularvelocity is not applied). In FIGS. 7A to 7C and FIGS. 8A to 8C, thehorizontal axis indicates time, and the vertical axis indicates voltage.In FIGS. 7A to 7C and FIGS. 8A to 8C, the solid line indicates thetemperature characteristics of the angular velocity signal 36 a, and thebroken line indicates the temperature characteristics of the vibrationleakage signal 36 b.

In FIGS. 7A, 7B, and 7C, the temperature characteristic curve of theangular velocity signal 36 a is similar to the temperaturecharacteristic curve of the vibration leakage signal 36 b. In FIGS. 8A,8B, and 8C, the temperature characteristic curve of the angular velocitysignal 36 a is similar to the temperature characteristic curve of thevibration leakage signal 36 b if the voltage value of the vibrationleakage signal 36 b is inverted with respect to the reference voltageV_(ref). However, the difference in voltage between the temperaturecharacteristic curve of the angular velocity signal 36 a and thetemperature characteristic curve of the vibration leakage signal 36 bvaries depending on the sample. The temperature characteristics of theangular velocity signal 36 a can be corrected using the vibrationleakage signal 36 b taking account of the similarity between thetemperature characteristics of the angular velocity signal 36 a and thetemperature characteristics of the vibration leakage signal 36 b.

FIG. 9 is a diagram illustrating a configuration example of anadder-subtractor circuit 370 that can correct the temperaturecharacteristics of the angular velocity signal 36 a. As illustrated inFIG. 9, the adder-subtractor circuit 370 may include a switch circuit372, an inverting amplifier 374, a variable gain amplifier 376, and anadder 378, for example.

The switch circuit 372 selects whether to input the vibration leakagesignal 36 b to the inverting amplifier 374 or the variable gainamplifier 376 based on a selection signal 52. For example, a switchsetting bit may be stored in the memory 50, and the switch setting bitmay be supplied to the switch circuit 372 as the selection signal 52.When the vibration leakage signal 36 b is input to the invertingamplifier 374, the vibration leakage signal 36 b is inverted in polarityby the inverting amplifier 374 (i.e., the voltage value is inverted withrespect to the reference voltage V_(ref)), and input to the variablegain amplifier 376. Specifically, the switch circuit 372 selects whetheror not to bypass the inverting amplifier 374. Whether to input thevibration leakage signal 36 b directly to the variable gain amplifier376, or input a signal obtained by inverting the polarity of thevibration leakage signal 36 b to the variable gain amplifier 376 can beselected using the switch circuit 372.

The variable gain amplifier 376 is an inverting amplifier that amplifiesor attenuates the input signal by a gain based on the selection signal54. For example, gain setting data may be stored in the memory 50, andeach bit of the gain setting data may be supplied to the variable gainamplifier 376 as the selection signal 52.

The adder 378 adds the angular velocity signal 36 a to the signal outputfrom the variable gain amplifier 376 to generate an angular velocitysignal 37.

When the adder-subtractor circuit 370 has the configuration illustratedin FIG. 9, and the temperature characteristics of the angular velocitysignal 36 a are similar to the temperature characteristics of thevibration leakage signal 36 b as illustrated in FIGS. 7A to 7C, thetemperature characteristics of the angular velocity signal 37 can bemade almost flat by setting the selection signal 52 so that the switchcircuit 372 bypasses the inverting amplifier 374, and selecting anappropriate value as the gain of the variable gain amplifier 376 usingthe selection signal 54. For example, when the angular velocity signal36 a (signal at the point H in FIG. 1) has temperature characteristicsillustrated in FIG. 10A, and the vibration leakage signal 36 b (signalat the point J in FIG. 1) has temperature characteristics illustrated inFIG. 10B, the vibration leakage signal 36 b is input to the variablegain amplifier 376, and inverted in polarity. Therefore, the signaloutput from the variable gain amplifier 376 (output signal at the pointK in FIG. 9) has temperature characteristics illustrated in FIG. 10C.Accordingly, the angular velocity signal 37 (output signal at the pointL in FIGS. 1 and 9) obtained by adding the angular velocity signal 36 a(signal at the point H in FIG. 1) to the signal output from the variablegain amplifier 376 (output signal at the point K in FIG. 9) using theadder 378 has temperature characteristics illustrated in FIG. 10D.

When the temperature characteristics of the angular velocity signal 36 aand the temperature characteristics of the vibration leakage signal 36 bhave the relationship illustrated in FIGS. 8A to 8C, the temperaturecharacteristics of the angular velocity signal 37 can be made almostflat by setting the selection signal 52 so that the switch circuit 372does not bypass the inverting amplifier 374, and selecting anappropriate value as the gain of the variable gain amplifier 376 usingthe selection signal 54. For example, when the angular velocity signal36 a (signal at the point H in FIG. 1) has temperature characteristicsillustrated in FIG. 11A, and the vibration leakage signal 36 b (signalat the point J in FIG. 1) has temperature characteristics illustrated inFIG. 11B, the vibration leakage signal 36 b is inverted in polarity bythe inverting amplifier 374, and inverted in polarity by the variablegain amplifier 376. Therefore, the signal output from the variable gainamplifier 376 (output signal at the point K in FIG. 9) has temperaturecharacteristics illustrated in FIG. 11C. Accordingly, the angularvelocity signal 37 (output signal at the point L in FIGS. 1 and 9)obtained by adding the angular velocity signal 36 a (signal at the pointH in FIG. 1) to the signal output from the variable gain amplifier 376(output signal at the point K in FIG. 9) using the adder 378 hastemperature characteristics illustrated in FIG. 11D.

According to the angular velocity detection apparatus according to thefirst embodiment, when the temperature characteristic curve of theangular velocity signal 36 a is similar to the temperaturecharacteristic curve of the vibration leakage signal 36 b, thetemperature characteristic curve of the angular velocity signal 37 canbe made almost flat by inverting the polarity of the vibration leakagesignal 36 b, and adding the resulting signal to the angular velocitysignal 36 a in a given ratio. When the temperature characteristic curveof the angular velocity signal 36 a is opposite to the temperaturecharacteristic curve of the vibration leakage signal 36 b, thetemperature characteristic curve of the angular velocity signal 37 canbe made almost flat by adding the vibration leakage signal 36 b to theangular velocity signal 36 a in a given ratio without inverting thepolarity of the vibration leakage signal 36 b. When the temperaturecharacteristic curve of the angular velocity signal 36 a differs fromthe temperature characteristic curve of the vibration leakage signal 36b, an optimum gain at which the temperature characteristic curve of theangular velocity signal 37 becomes almost flat can be selected byallowing the gain of the variable gain amplifier 376 to be adjustable.

Specifically, the angular velocity detection apparatus according to thefirst embodiment can compensate for a change in temperaturecharacteristics of the angular velocity signal due to the vibrationleakage component of the vibrator without using a higher-ordertemperature compensation circuit.

When using the configuration illustrated in FIG. 9, the switch circuit372 and the inverting amplifier 374 may be provided in the subsequentstage of the variable gain amplifier 376. Alternatively, a non-invertingamplifier may be used as the variable gain amplifier 376 so that thelogic of the selection signal 52 input to the switch circuit 372 is thereverse of that illustrated in FIG. 9. The configuration illustrated inFIG. 1 may be modified so that the signal output from the synchronousdetection circuit 350 and the signal output from the synchronousdetection circuit 352 are input to the adder-subtractor circuit 370, andthe integration circuit 360 is disposed in the subsequent stage of theadder-subtractor circuit 370.

1-2. Second Embodiment

In the examples illustrated in FIGS. 7A to 7C and FIGS. 8A to 8C, thetemperature characteristics of the angular velocity signal 36 a issimilar to the temperature characteristics of the vibration leakagesignal 36 b. FIG. 12 illustrates an example of temperaturecharacteristics that differ in tendency from those illustrated in FIGS.7A to 7C and FIGS. 8A to 8C. In FIG. 12, the horizontal axis indicatestime, and the vertical axis indicates voltage. In FIG. 12, the solidline indicates the temperature characteristics of the angular velocitysignal 36 a, and the broken line indicates the temperaturecharacteristics of the vibration leakage signal 36 b.

In FIG. 12, the temperature characteristics of the angular velocitysignal 36 a and the temperature characteristics of the vibration leakagesignal 36 b differ in second-order component and third-order componentto only a small extent, but differ in first-order component to a largeextent. Therefore, the temperature characteristics of the angularvelocity signal 37 do not become flat even if the angular velocitysignal 36 a and the vibration leakage signal 36 b are input to theadder-subtractor circuit 370. In this case, it is considered to beeffective to input the angular velocity signal 36 a and the vibrationleakage signal 36 b to the adder-subtractor circuit 370 (i.e., subjectedto addition or subtraction) after adjusting the first-order component ofthe temperature characteristics of the angular velocity signal 36 a andthe first-order component of the temperature characteristics of thevibration leakage signal 36 b to a similar value.

FIG. 13 is a diagram illustrating a configuration example of an angularvelocity detection apparatus according to a second embodiment of theinvention. In FIG. 13, the same sections as those illustrated in FIG. 1are indicated by the same symbols. Description of these sections isomitted.

An angular velocity detection apparatus 1 according to the secondembodiment includes first-order temperature adjustment circuits 390 and392 in addition to the configuration illustrated in FIG. 1. The angularvelocity detection apparatus 1 according to the second embodiment alsoincludes a temperature sensor 70. Note that the temperature sensor 70may be provided outside the angular velocity detection IC 10.

The temperature sensor 70 outputs a temperature detection signal 72 thathas a linear voltage value with respect to the temperature. Thetemperature detection signal 72 is input to the first-order temperatureadjustment circuits 390 and 392.

The first-order temperature adjustment circuit 390 adjusts thefirst-order component of the temperature characteristics of the angularvelocity signal 36 a to approach a first value using the temperaturedetection signal 72. The first-order temperature adjustment circuit 392adjusts the first-order component of the temperature characteristics ofthe vibration leakage signal 36 b to approach a second value using thetemperature detection signal 72. The first value may be the same as thesecond value. For example, when the first value and the second value are0, the first-order temperature adjustment circuit 390 functions as afirst-order temperature correction circuit that cancels the first-ordercomponent of the temperature characteristics of the angular velocitysignal 36 a, and the first-order temperature adjustment circuit 392functions as a first-order temperature correction circuit that cancelsthe first-order component of the temperature characteristics of thevibration leakage signal 36 b. Note that a value other than 0 may beselected as the first value and the second value.

The first-order temperature adjustment circuits 390 and 392 may beimplemented by circuits having the same configuration. FIG. 14 is adiagram illustrating a configuration example of the first-ordertemperature adjustment circuit 390 (392). As illustrated in FIG. 14, thefirst-order temperature adjustment circuit 390 (392) may include aswitch circuit 394, an inverting amplifier 395, a variable gainamplifier 396, and an adder 397, for example.

The switch circuit 394 selects whether to input the temperaturedetection signal 72 to the inverting amplifier 395 or the variable gainamplifier 396 based on a selection signal 56. For example, a switchsetting bit may be stored in the memory 50, and the switch setting bitmay be supplied to the switch circuit 394 as the selection signal 56.When the temperature detection signal 72 is input to the invertingamplifier 395, the temperature detection signal 72 is inverted inpolarity by the inverting amplifier 395, and input to the variable gainamplifier 396. Specifically, the switch circuit 394 selects whether ornot to bypass the inverting amplifier 395. Whether to input thetemperature detection signal 72 directly to the variable gain amplifier396, or input a signal obtained by inverting the polarity of thetemperature detection signal 72 to the variable gain amplifier 396 canbe selected using the switch circuit 394.

The variable gain amplifier 396 is an inverting amplifier that amplifiesor attenuates the input signal by a gain based on the selection signal58. For example, gain setting data may be stored in the memory 50, andeach bit of the gain setting data may be supplied to the variable gainamplifier 396 as the selection signal 58.

The adder 397 adds the angular velocity signal 36 a or the vibrationleakage signal 36 b to the signal output from the variable gainamplifier 396 to generate an angular velocity signal 39 a or a vibrationleakage signal 39 b.

The angular velocity signal 39 a and the vibration leakage signal 39 bare input to the adder-subtractor circuit 370 having the configurationillustrated in FIG. 9, for example. The angular velocity signal 37having corrected temperature characteristics is thus generated.

Note that the first-order temperature adjustment circuits 390 and 392function as a first first-order temperature adjustment section and asecond first-order temperature adjustment section, respectively.

When the first-order temperature adjustment circuit 390 (392) has theconfiguration illustrated in FIG. 14, the selection signal 56 is set sothat the switch circuit 394 bypasses the inverting amplifier 395 whenthe polarity (positive or negative) of the slope (first-order component)of the temperature characteristics of the angular velocity signal 36 a(vibration leakage signal 36 b) is the same as the polarity (positive ornegative) of the slope of the temperature detection signal 72 withrespect to the temperature. The selection signal 56 is set so that theswitch circuit 394 does not bypass the inverting amplifier 395 when thepolarity (positive or negative) of the slope (first-order component) ofthe temperature characteristics of the angular velocity signal 36 a(vibration leakage signal 36 b) is the reverse of the polarity (positiveor negative) of the slope of the temperature detection signal 72 withrespect to the temperature. The first-order component of the temperaturecharacteristics of the angular velocity signal 39 a (vibration leakagesignal 39 b) approaches the first value (second value) as a result ofselecting an appropriate value as the gain of the variable gainamplifier 396 by appropriately setting the selection signal 58.

For example, when the angular velocity signal 36 a (signal at the pointH in FIG. 13) has temperature characteristics illustrated in FIG. 15A(solid line), the vibration leakage signal 36 b (signal at the point Jin FIG. 13) has temperature characteristics illustrated in FIG. 15B(solid line), and the temperature detection signal 72 (signal at thepoint Z in FIG. 13) has a negative slope with respect to the temperatureas illustrated in FIG. 15C, since the first-order component of thetemperature characteristics of the angular velocity signal 36 a ispositive (broken line in FIG. 15A), the temperature detection signal 72is input to the adder 397 via the variable gain amplifier 396 and thevariable gain amplifier 396 of the first-order temperature adjustmentcircuit 390. The angular velocity signal 39 a (signal at the point M inFIG. 13) thus has temperature characteristics illustrated in FIG. 15D(i.e., the first-order component (broken line in FIG. 15D) is adjustedto the first value (e.g., 0)). Since the first-order component of thetemperature characteristics of the vibration leakage signal 36 b isnegative (broken line in FIG. 15B), the temperature detection signal 72is input to the adder 397 via the variable gain amplifier 396 of thefirst-order temperature adjustment circuit 390. The vibration leakagesignal 36 b (signal at the point N in FIG. 13) thus has temperaturecharacteristics illustrated in FIG. 15E (i.e., the first-order component(broken line in FIG. 15E) is adjusted to the second value (e.g., 0)).The angular velocity signal 39 a (signal at the point M in FIG. 13) andthe vibration leakage signal 39 b (signal at the point N in FIG. 13) arethen input to the adder-subtractor circuit 370, so that the angularvelocity signal 37 (signal at the point L in FIG. 13) having almost flattemperature characteristics (see FIG. 15F) is generated.

According to the angular velocity detection apparatus according to thesecond embodiment, even if the first-order component of the temperaturecharacteristics of the angular velocity signal 36 a differs from thefirst-order component of the temperature characteristics of thevibration leakage signal 36 b, the first-order component of thetemperature characteristics of the angular velocity signal 36 a and thefirst-order component of the temperature characteristics of thevibration leakage signal 36 b can be adjusted to approach (ideallycoincide) using the first-order temperature adjustment circuits 390 and392, and the temperature characteristics of the angular velocity signalcan then be corrected by the adder-subtractor circuit 370. This makes itpossible to correct various combinations of the first-order component ofthe temperature characteristics of the angular velocity signal 36 a andthe first-order component of the temperature characteristics of thevibration leakage signal 36 b as compared with the first embodiment.

When using the configuration illustrated in FIG. 14, the switch circuit394 and the inverting amplifier 395 may be provided in the subsequentstage of the variable gain amplifier 396. Alternatively, a non-invertingamplifier may be used as the variable gain amplifier 396 so that thelogic of the selection signal 56 input to the switch circuit 394 is thereverse of that illustrated in FIG. 14. In FIG. 13, the first-ordertemperature adjustment circuit 390 may be disposed between thesynchronous detection circuit 350 and the integration circuit 360.Likewise, the first-order temperature adjustment circuit 392 may bedisposed between the synchronous detection circuit 352 and theintegration circuit 362.

1-3. Third Embodiment

FIG. 16 is a diagram illustrating a configuration example of an angularvelocity detection apparatus according to a third embodiment of theinvention. In FIG. 16, the same sections as those illustrated in FIG. 13are indicated by the same symbols. Description of these sections isomitted.

An angular velocity detection apparatus 1 according to the thirdembodiment has a configuration in which the first-order temperatureadjustment circuit 390 is omitted from the configuration illustrated inFIG. 13. The first-order temperature adjustment circuit 392 adjusts thefirst-order component of the temperature characteristics of thevibration leakage signal 36 b to approach the first-order component ofthe temperature characteristics of the angular velocity signal 36 abased on the temperature detection signal 72. The first-ordertemperature adjustment circuit 392 may be configured in the same manneras in FIG. 14. The first-order temperature adjustment circuit 392functions as a first-order temperature adjustment section.

When the angular velocity signal 36 a (signal at the point H in FIG. 16)has temperature characteristics illustrated in FIG. 17A (solid line),the vibration leakage signal 36 b (signal at the point J in FIG. 16) hastemperature characteristics illustrated in FIG. 17B (solid line), andthe temperature detection signal 72 (signal at the point Z in FIG. 16)has a negative slope with respect to the temperature as illustrated inFIG. 17C, the temperature detection signal 72 is input to the adder 397via the variable gain amplifier 396 (i.e., the temperature detectionsignal 72 is inverted in polarity, and then added to the vibrationleakage signal 36 b by the adder 397). The vibration leakage signal 36 b(signal at the point N in FIG. 16) thus has temperature characteristicsillustrated in FIG. 15D (i.e., the first-order component (broken line inFIG. 17D) of the temperature characteristics of the vibration leakagesignal 36 b approaches the first-order component (broken line in FIG.17A) of the temperature characteristics of the angular velocity signal36 a (signal at the point H in FIG. 16)). The angular velocity signal 36a (signal at the point H in FIG. 16) and the vibration leakage signal 39b (signal at the point N in FIG. 16) are then input to theadder-subtractor circuit 370, so that the angular velocity signal 37(signal at the point L in FIG. 16) having almost flat temperaturecharacteristics (see FIG. 17E) is generated.

According to the angular velocity detection apparatus according to thethird embodiment, even if the first-order component of the temperaturecharacteristics of the angular velocity signal 36 a differs from thefirst-order component of the temperature characteristics of thevibration leakage signal 36 b, the first-order component of thetemperature characteristics of the vibration leakage signal 36 b can beadjusted to approach (ideally coincide with) the first-order componentof the temperature characteristics of the angular velocity signal 36 ausing the first-order temperature adjustment circuit 392, and thetemperature characteristics of the angular velocity signal can then becorrected by the adder-subtractor circuit 370. This makes it possible tocorrect various combinations of the first-order component of thetemperature characteristics of the angular velocity signal 36 a and thefirst-order component of the temperature characteristics of thevibration leakage signal 36 b as compared with the first embodiment.

In FIG. 16, the first-order temperature adjustment circuit 392 may bedisposed between the synchronous detection circuit 352 and theintegration circuit 362. The first-order temperature adjustment circuit392 may be disposed between the integration circuit 360 and theadder-subtractor circuit 370, or disposed between the synchronousdetection circuit 350 and the integration circuit 360 so that thefirst-order component of the temperature characteristics of the angularvelocity signal approaches the first-order component of the temperaturecharacteristics of the vibration leakage signal.

1-4. Fourth Embodiment

FIG. 18 is a diagram illustrating a configuration example of an angularvelocity detection apparatus according to a fourth embodiment of theinvention. In FIG. 18, the same sections as those illustrated in FIG. 13are indicated by the same symbols. Description of these sections isomitted.

An angular velocity detection apparatus 1 according to the fourthembodiment differs from the configuration illustrated in FIG. 13 in thatthe first-order temperature adjustment circuits 390 and 392 are omitted,and a first-order temperature correction circuit 398 is added in thesubsequent stage of the adder-subtractor circuit 370. The first-ordertemperature correction circuit 398 corrects the first-order component ofthe temperature characteristics of the angular velocity signal 37 basedon the temperature detection signal 72. The first-order temperaturecorrection circuit 398 may be configured in the same manner as in FIG.14. The first-order temperature correction circuit 398 functions as afirst-order temperature correction section.

When the angular velocity signal 36 a (signal at the point H in FIG. 18)has temperature characteristics illustrated in FIG. 19A (solid line),the vibration leakage signal 36 b (signal at the point J in FIG. 18) hastemperature characteristics illustrated in FIG. 19B (solid line), andthe temperature detection signal 72 (signal at the point Z in FIG. 18)has a negative slope with respect to the temperature as illustrated inFIG. 19C, the vibration leakage signal 36 b is directly input to thevariable gain amplifier 376. Therefore, the signal output from thevariable gain amplifier 376 (output signal at the point K in FIG. 19)has temperature characteristics illustrated in FIG. 19D (i.e., thetemperature characteristics of the vibration leakage signal 36 b (FIG.19B) that have been inverted in polarity, and amplified or attenuatedbased on the gain of the variable gain amplifier 376). Accordingly, theangular velocity signal 37 (output signal at the point L in FIGS. 1 and9) obtained by adding the angular velocity signal 36 a to the signaloutput from the variable gain amplifier 376 using the adder 378 hastemperature characteristics illustrated in FIG. 19E (i.e., second andhigher order components are almost canceled while the first-ordercomponent remains). The angular velocity signal 39 c (signal at thepoint O in FIG. 18) obtained by correcting the first-order component ofthe temperature characteristics of the angular velocity signal 37 usingthe first-order temperature correction circuit 398 has almost flattemperature characteristics illustrated in FIG. 19F.

According to the angular velocity detection apparatus according to thefourth embodiment, even if the first-order component of the temperaturecharacteristics of the angular velocity signal 36 a differs from thefirst-order component of the temperature characteristics of thevibration leakage signal 36 b, the first-order component of thetemperature characteristics of the angular velocity signal that stillremains uncorrected after temperature correction by the adder-subtractorcircuit 370 can be corrected by the first-order temperature correctioncircuit 398. This makes it possible to correct various combinations ofthe first-order component of the temperature characteristics of theangular velocity signal 36 a and the first-order component of thetemperature characteristics of the vibration leakage signal 36 b ascompared with the first embodiment.

2. ELECTRONIC INSTRUMENT

FIG. 20 is a functional block diagram illustrating a configurationexample of an electronic instrument according to one embodiment of theinvention. An electronic instrument 500 according to this embodimentincludes an angular velocity detection apparatus 600, a CPU 700, anoperation section 710, a display section 720, a read-only memory (ROM)730, a random access memory (RAM) 740, and a communication section 750.Note that the electronic instrument according to this embodiment mayhave a configuration in which some of the elements (sections)illustrated in FIG. 20 are omitted, or other elements are additionallyprovided.

The angular velocity detection apparatus 600 generates an angularvelocity signal having a voltage corresponding to the angular velocity,and outputs the angular velocity signal to the CPU 700. The angularvelocity detection apparatus 600 may generate a vibration leakage signalhaving a voltage corresponding to the magnitude of vibration leakage dueto excited vibrations of a vibrator, and may output the vibrationleakage signal to the CPU 700.

The CPU 700 performs a calculation process and a control process basedon a program stored in the ROM 730. Specifically, the CPU 700 controlsthe angular velocity detection apparatus 600, or receives the angularvelocity signal or the like from the angular velocity detectionapparatus 600, and performs a calculation process. The CPU 700 performsa process corresponding to an operation signal from the operationsection 710, transmits a display signal for displaying information onthe display section 720, and controls the communication section 750performing data communication with the outside, for example.

The operation section 710 is an input device including an operation key,a button switch, and the like, and outputs an operation signal based onan operation performed by the user to the CPU 700.

The display section 720 is a display device such as a liquid crystaldisplay (LCD), and displays information based on the display signalinput from the CPU 700.

The ROM 730 stores a program that causes the CPU 700 to perform acalculation process and a control process, a program that implements anavigation function or the like, data, and the like.

The RAM 740 is used as a work area for the CPU 700. The RAM 740temporarily stores a program and data read from the ROM 730, data inputfrom the operation section 710, the results of calculations performed bythe CPU 700 based on a program, and the like.

The communication section 750 performs a control process that implementsdata communication between the CPU 700 and an external device.

A process with relatively high accuracy can be implemented at low costby incorporating the angular velocity detection apparatus according toany of the above embodiments in the electronic instrument 500 as theangular velocity detection apparatus 600.

The electronic instrument 600 may be an arbitrary electronic instrumentthat utilizes the angular velocity detection apparatus. For example, theelectronic instrument 600 may be a vehicular antiskid brake system, avehicular overturn detection apparatus, a mobile phone, a navigationsystem, a pointing device such as a mouse, a digital camera, a gamecontroller, or the like.

The invention is not limited to the above embodiments. Variousmodifications and variations may be made without departing from thescope of the invention.

The invention includes various other configurations substantially thesame as the configurations described in connection with the aboveembodiments (e.g., a configuration having the same function, method, andresults, or a configuration having the same objective and effects). Theinvention also includes a configuration in which an unsubstantialsection (element) described in connection with the above embodiments isreplaced by another section (element). The invention also includes aconfiguration having the same effects as those of the configurationsdescribed in connection with the above embodiments, or a configurationcapable of achieving the same objective as that of the configurationsdescribed in connection with the above embodiments. The invention alsoincludes a configuration in which a known technique is added to theconfigurations described in connection with the above embodiments.

Although only some embodiments of the invention have been described indetail above, those skilled in the art would readily appreciate thatmany modifications are possible in the embodiments without materiallydeparting from the novel teachings and advantages of the invention.Accordingly, such modifications are intended to be included within thescope of the invention.

What is claimed is:
 1. An angular velocity detection circuit that isconnected to a resonator for generating a signal that includes anangular velocity component corresponding to a magnitude of an angularvelocity, and a vibration leakage component of vibrations based on adrive signal, the angular velocity detection circuit comprising: adriver section that generates the drive signal, and supplies the drivesignal to the vibrator; an angular velocity signal generation sectionthat extracts the angular velocity component from the signal generatedby the vibrator, and generates an angular velocity signal correspondingto the magnitude of the angular velocity; a vibration leakage signalgeneration section that extracts the vibration leakage component fromthe signal generated by the vibrator, and generates a vibration leakagesignal corresponding to the magnitude of the vibration leakage; and acorrecting section that corrects temperature characteristics of theangular velocity signal based on the vibration leakage signal to theangular velocity signal.
 2. The angular velocity detection circuit asdefined in claim 1, further comprising: the correcting section includingan adder-subtractor section that adds the vibration leakage signal tothe angular velocity signal, or subtracts the vibration leakage signalfrom the angular velocity signal, in a given ratio to correcttemperature characteristics of the angular velocity signal.
 3. Theangular velocity detection circuit as defined in claim 2, furthercomprising: a first first-order temperature adjustment section thatadjusts a first-order component of the temperature characteristics ofthe angular velocity signal input to the adder-subtractor section toapproach a first value; and a second first-order temperature adjustmentsection that adjusts a first-order component of temperaturecharacteristics of the vibration leakage signal input to theadder-subtractor section to approach a second value.
 4. The angularvelocity detection circuit as defined in claim 2, further comprising: afirst-order temperature adjustment section that adjusts one of afirst-order component of the temperature characteristics of the angularvelocity signal input to the adder-subtractor section and a first-ordercomponent of temperature characteristics of the vibration leakage signalinput to the adder-subtractor section to approach the other of thefirst-order component of the temperature characteristics of the angularvelocity signal and the first-order component of the temperaturecharacteristics of the vibration leakage signal.
 5. The angular velocitydetection circuit as defined in claim 2, further comprising: afirst-order temperature correction section that corrects a first-ordercomponent of temperature characteristics of a signal obtained by theadder-subtractor section.
 6. The angular velocity detection circuit asdefined in claim 2, further comprising: a terminal that outputs a signalbased on the vibration leakage signal to the outside.
 7. The angularvelocity detection circuit as defined in claim 2, further comprising: afailure determination section that determines the presence or absence offailure of the angular velocity detection circuit based on the vibrationleakage signal.
 8. The angular velocity detection circuit as defined inclaim 2, the adder-subtractor section including an inverting amplifierthat inverts a polarity of an input signal, a switch circuit thatselects whether or not to bypass the inverting amplifier, and a variablegain amplifier that is disposed in series with the inverting amplifier,and amplifies or attenuates an input signal by a gain that can bevariably set, the adder-subtractor section selecting whether or not toadd a signal obtained by inverting a polarity of the vibration leakagesignal to the angular velocity signal using the inverting amplifier andthe switch circuit, and selecting a ratio of the vibration leakagesignal added to the angular velocity signal using the variable gainamplifier.